Adhesive sheet, reinforcing repair tape, and reinforced building material

ABSTRACT

The present invention is to provide an adhesive sheet having superior workability and instantly exhibiting stable, high-level reinforcing/repairing performance when bonded to an adherend such as a building material. An adhesive sheet according to the present invention comprises a substrate layer comprising reinforcing fibers impregnated with an acidic resin and a basic adhesive layer disposed upon the substrate layer.

FIELD OF THE INVENTION

The present disclosure relates to an adhesive sheet capable of beingused to reinforce and repair an adherend. More specifically, the presentdisclosure relates to an adhesive sheet and a reinforcing repair tapesuitable for reinforcing and repairing a building material, and to abuilding material reinforced using the reinforcing repair tape.

BACKGROUND ART

Reinforcing fiber sheets of carbon fibers or the like are generallybonded to structural materials, such as concrete used as a buildingmaterial or sheet steel used for automobile exteriors, in order toreinforce or repair the same.

One method of reinforcing concrete building materials, such as concretepillars, is to wrap them in fiber-reinforced plastic (FRP). Such methodsof wrapping in FRP require numerous work steps, such as treating thesubstrate by grinding away degraded parts of the concrete surface,applying an epoxy adhesive primer, fixing irregularities in the surfaceof the concrete, applying a base coat of epoxy adhesive, wrapping FRPsheets containing reinforcing fibers such as carbon fibers or aramidfibers, applying a top coat of epoxy adhesive so as to impregnate theFRP sheet, and curing. The epoxy adhesive preferably has a long workingtime so as to allow the builder to adjust the bonding position after theFRP sheet has been wrapped around the concrete pillar. Thus, the timeneeded to wrap and cure one FRP sheet is generally at least one day, anda working period of at least two days is necessary if a plurality of FRPsheets are wrapped.

Japanese Unexamined Patent Application Publication No. H08-218646Adiscloses a “method of reinforcing a concrete structure by removing andrepairing damaged sections in and cleaning the surface of apillar-shaped concrete structure, followed by applying a primer to thesurface and curing, evenly applying an adhesive to the surface, thenwrapping and bonding a concrete structure-reinforcing tape around thepillar-shaped concrete structure without any slack, chemical fibers ofgood softness and a tensile strength greater than that of concrete beingused for the lengthwise fibers of the tape and chemical fibers capableof fixing the position of the lengthwise fibers being used for thewidthwise fibers, the lengthwise chemical fibers being interwoven withthe widthwise fibers in a linearly arranged state, and a fiber space foractively forcing the adhesive to flow being woven between the front andback sides of the tape”.

Japanese Unexamined Patent Application Publication No. H10-259665Adiscloses a “method of reinforcing a building in which a release sheetof a high-strength fiber reinforcing sheet having a releasable adhesiveapplied to an entire rear surface thereof and a release sheet layeredthereupon is peeled off, the rear surface of the reinforcing sheet iscompressed and releasably bonded to the surface of a building, thereleasably bonded high-strength fiber reinforcing sheet is thenthoroughly impregnated with adhesive, and, finally, the surface of theimpregnated high-strength fiber reinforcing sheet is finished”.

Japanese Unexamined Patent Application Publication No. H10-311145Adiscloses a “reinforcing fiber sheet for a concrete structure in which aprimary sheet is releasably semi-bonded to a backing paper via anadhesive, wherein the backing paper is transparent or semi-transparent”.

Japanese Unexamined Patent Application Publication No. H11-062259Adiscloses a “reinforcing repair adhesive tape in which a reinforcingfiber sheet drawn into alignment in a single direction comprises a basecloth of rough woven fabric on at least one side thereof, and onesurface of the sheet comprises a layer of adhesive”.

Japanese Unexamined Patent Application Publication No. 2002-047809Adiscloses a “reinforced composite material obtained by first bonding acurable fiber-reinforced plastic (“pre-preg”) sheet comprising a layerof pressure-sensitive adhesive on one or both surfaces to apredetermined carrier using the layer of pressure-sensitive adhesive,followed by curing the pre-preg using an appropriate method; as well asa method of manufacturing and a method of applying the same”.

Japanese Unexamined Patent Application Publication No. H11-124955Adiscloses a “method of reinforcing a concrete pillar in which abelt-shaped reinforcing member of reinforcing fibers, such as aromaticpolyamide fibers, is wrapped around a concrete pillar, such as a bridgepier, provided near a wall surface, and the reinforcing fibers areimpregnated with resin to reinforce the concrete pillar; wherein a curedsection impregnated with resin and cured in advance is formed in acentral part of the lengthwise direction of the belt-shaped reinforcingmember, an adhesive is applied to one surface of the cured section,after which the reinforcing member is wrapped around so that the curedsection is positioned on a side surface of the concrete pillar facingthe wall and the cured section is applied to the side surface, the partsof the reinforcing member other than the cured section are impregnatedwith resin and applied to the pillar, and the resin is cured”.

Japanese Unexamined Patent Application Publication No. H11-050348Adiscloses a “reinforcing tape constituted by a reinforcing sheetconstituted by an elongated fiber sheet, marks being formed at constantintervals in the lengthwise direction”.

SUMMARY OF THE INVENTION

Because the FRP wrap method involves multiple onsite work steps, asdescribed above, it is labor-intensive and takes time to apply. Inaddition, in order to yield design strength, uniform tension must beapplied to the FRP sheet when being wrapped, and the quality of thefinished product is highly dependent upon the worker. Moreover, whenreinforcing or repairing railroad bridge piers, concrete pillars forbuildings housing restaurants or other shops, or the like, work time isoften limited to late at night, when the trains have stopped running orthe shops are closed. In addition, because the FRP wrap method is a wetmethod, it may exhibit problems such as uneven curing due to vibrationsfrom passing trains if a railroad bridge pier is reinforced or repaired,or unpleasant odors from the epoxy adhesive if construction is performednear a shop.

The present disclosure provides an adhesive sheet having superiorworkability and instantly exhibiting stable, high-levelreinforcing/repairing performance when bonded to an adherend such as abuilding material.

Means to Solve the Problem

In accordance with one embodiment of the present disclosure, an adhesivesheet is provided comprising a substrate layer comprising reinforcingfibers impregnated with an acidic resin and a basic adhesive layerdisposed upon the substrate layer.

In accordance with another embodiment of the present disclosure, areinforcing repair tape and a building material-reinforcing repair tapecomprising the adhesive sheet are provided.

In accordance with yet another embodiment of the present disclosure, areinforced building material around which the buildingmaterial-reinforcing repair tape is wrapped is provided.

Effect of the Invention

In the adhesive sheet according to the present disclosure, thereinforcing fiber-containing substrate layer and the adhesive layer areintegrally formed, yielding superior workability, and allowing designstrength to be obtained immediately after application.

In addition, the adhesive sheet according to the present disclosure isprovided with a substrate layer in which the reinforcing fibers arepre-impregnated with an acidic resin to form an integrated whole,allowing for the suppression of shifting that occurs between thereinforcing fibers and the acidic resin when stress is applied to theadhesive sheet. Moreover, the acid-base interaction between the acidicresin-containing substrate layer and the basic adhesive layer at theinterface of the two layers allows the two to strongly bond to eachother. The synergistic effects of these various features allows theadhesive sheet according to the present disclosure to exhibit a highlevel of shear strength in a direction parallel with the surface of theadhesive sheet.

The above descriptions should not be construed to be a disclosure of allof the embodiments and benefits of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an adhesive sheet according to oneembodiment of the present disclosure.

FIG. 2 is a perspective view of a concrete pillar reinforced by wrappinga reinforcing repair tape according to one embodiment of the presentdisclosure.

FIG. 3 is a cross-sectional view of a concrete pillar with a reinforcingrepair tape according to one embodiment of the present disclosurewrapped twice therearound.

FIG. 4 is a magnified view of the portion indicated by dotted lines inFIG. 3.

FIG. 5 is a chart illustrating a lining test (compression test) for afirst example and a first comparative example.

DETAILED DESCRIPTION OF THE INVENTION

A detailed description for the purpose of illustrating representativeembodiments of the present invention is given below, but theseembodiments should not be construed as limiting the present invention.

In the present disclosure, “(meth)acrylic” refers to “acrylic ormethacrylic”, and “(meth)acrylate” refers to “acrylate or methacrylate”.

An adhesive sheet according to one embodiment of the present disclosurecomprises a substrate layer comprising reinforcing fibers impregnatedwith an acidic resin and a basic adhesive layer disposed upon thesubstrate layer.

A cross-sectional view of an adhesive sheet according to an embodimentof the present disclosure is illustrated in FIG. 1. An adhesive sheet 10comprises a substrate layer 12 and a layer of basic adhesive 18 disposedthereupon. The substrate layer 12 comprises reinforcing fibers 14, andthe reinforcing fibers 14 are impregnated with an acidic resin 16.

The reinforcing fibers serve as a scaffold for the substrate layer, andare a primary element in determining the strength of the adhesive sheet.Carbon fibers, glass fibers, and other inorganic continuous fibers,aromatic polyamide fibers (aramid fibers), nylon fibers, vinylon fibers,polyester fibers, polyparaphenylene benzoxazole (PBO) fibers,high-strength polyethylene fibers, and other organic continuous fibers,and combinations thereof can be used as the reinforcing fibers. Carbonfibers and aramid fibers are advantageously used due to their highstrength, and carbon fibers are especially advantageous due to theirlight weight.

The reinforcing fibers may be drawn and aligned in one direction, or maybe woven or knitted into a plain weave, twill, heavy twill, satin, orother type of sheet. Both the warp and the filling fibers may beconstituted by reinforcing fibers, or another type of fiber may be usedfor one. Plain weave or twill sheets are generally used, as they areeasily obtainable. The width of the reinforcing fiber sheet may varyaccording to application; for instance, if the sheet is used toreinforce or repair a concrete building material, the width of the sheetis generally about 200 mm or greater, about 250 mm or greater, or about300 mm or greater and about 1,500 mm or less, about 1,000 mm or less, orabout 800 mm or less out of considerations of workability, efficiency,and the like.

The mass (also referred to as “fabric weight” or “basis weight”) of thereinforcing fiber sheet is generally about 50 g/m² or more, about 100g/m² or more, or about 150 g/m² or more, and about 1,000 g/m² or less,about 800 g/m² or less, or about 500 g/m² or less. The thickness of thereinforcing fiber sheet can be selected out of consideration for therequired reinforcing/repairing strength and workability, and isgenerally about 0.05 mm or more, about 0.1 mm or more, or about 0.15 mmor more, and about 1 mm or less, about 0.8 mm or less, or about 0.5 mmor less.

The fiber diameter of the reinforcing fibers is generally about 0.05 mmor more, about 0.08 mm or more, or about 0.10 mm or more, and about 1.20mm or less, about 0.70 mm or less, or about 0.35 mm. The tensilestrength of the reinforcing fibers is selected according to application,and will generally be about 0.01 kN/mm² or more, about 0.1 kN/mm² ormore, or about 1.0 kN/mm² or more, and about 100 kN/mm² or less, about50 kN/mm² or less, or about 20 kN/mm² or less as measured according toJIS A 1191:2004, “Test method for tensile properties of fiber reinforcedpolymer (FRP) sheets for reinforcement of concrete”. The breakingelongation of the reinforcing fibers is generally about 0% or more,about 0.2% or more, or about 0.5% or more and about 10% or less, about8% or less, or about 6% or less as measured according to JIS A1191:2004, “Test method for tensile properties of fiber reinforcedpolymer (FRP) sheets for reinforcement of concrete”. Generally,reinforcing fibers used for reinforcing purposes are required to resistelongation and have high tensile strength; thus, carbon fibers, aramidfibers, or a combination thereof is preferable.

The acidic resin impregnates the reinforcing fibers to form a matrix forthe substrate layer, and is an element imparting additional strength tothe adhesive sheet. In the present disclosure, “acidic” refers to thematerial having sites having the property of accepting electron pairs asan electron pair acceptor (i.e., being a Lewis acid), or having siteshaving the property of forming a conjugate acid with added hydrogenions. In the present disclosure, “basic” refers to the substance havingsites having the property of donating electron pairs as an electron pairdonor (i.e., being a Lewis base), or having sites having the property offorming a conjugate base with detached hydrogen ions. In the presentdisclosure, “acidic” and “basic” are relative concepts dependent uponthe material constituting the object of comparison. For example, amaterial having both sites functioning as a Lewis acid and sitesfunctioning as a Lewis base will function as a basic material if anothermaterial adjacent to the material is acidic, and will function as anacidic material if another material adjacent to the material is basic;thus, it can be applied, as appropriate, to either the acidic resin orthe basic adhesive to be described hereafter.

Various polymer materials comprising active hydrogen-containingfunctional groups, such as carboxyl groups, hydroxyl groups, sulfonicacid groups, sulfuric acid groups, phosphonic acid groups, phosphoricacid groups, or the like, can be used as the acidic resin. A polymermaterial comprising a functional group that, while not containing activehydrogen, serves to impart the material with acidity as defined above,such as a carboxylate group, can also be used as the acidic resin.

The acidic resin may be any of a thermoplastic resin, a thermoset resin,or a radiation-curing resin. Examples of the acceptable polymer materialused as acidic resins include (meth)acrylic resin, epoxy resin,polyester, polyurethane, polypropylene, ethylene-vinyl acetatecopolymer, polyvinyl chloride, polyvinylidene chloride, silicone resin,and the like. If the adhesive sheet is applied to a curved surface, theacidic resin is advantageously an elastomer having visco-elasticproperties. If the acidic resin is an elastomer, the reinforcing effectsof the adhesive sheet can suppress rapid degradation arising frombrittle failure of the acidic resin.

The glass transition temperature (Tg) of the acidic resin is generallyabout −60° C. or higher, about −40° C. or higher, or about 0° C. orhigher, and about 200° C. or lower, about 100° C. or lower, or about 50°C. or lower. The Tg is determined via differential scanning calorimetry(DSC). The strength and rigidity of the adhesive sheet will increase,improving reinforcing/repairing performance, as the Tg increases, butsoftness will decrease, potentially reducing stress relaxationproperties, conformity to curved surfaces, workability, and the like.

A favorable example of an acidic resin is acidic (meth)acrylic resin.(Meth)acrylic resin can be obtained by polymerizing an alkyl(meth)acrylate monomer having from 1 to 30 carbons at the ester site, aswell as an active hydrogen-containing acidic monomer and/or acrosslinking agent-containing mixture as necessary. Polymerization canbe performed via thermal polymerization or photopolymerization. Examplesof possible initiators include thermal polymerization initiators knownin the art, such as benzoyl peroxide and azobis isobutyronitrile (AIBN),or photoinitiators, such as benzophenone and 2,2-dimethoxy-2-phenylacetophenone.

Examples of alkyl (meth)acrylate monomers having from 1 to 30 carbons atthe ester site include methyl (meth)acrylate, ethyl (meth)acrylate,n-butyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl(meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and otheralkyl (meth)acrylates; phenyl (meth)acrylate; methoxypropyl(meth)acrylate, 2-methoxybutyl (meth)acrylate, and other alkoxyalkyl(meth)acrylates; and phenoxyethyl (meth)acrylate and other phenoxyalkyl(meth)acrylates. One or more types of these can be used in order toobtain the desired glass transition temperature, tensile strength,elongation properties, and the like. Alkyl ester groups derived fromthese monomers exhibit acidity.

Examples of active hydrogen-containing acidic monomers include(meth)acrylic acid, maleic acid, itaconic acid, ω-carboxypolycaprolactone monoacrylate, phthalic acid mono hydroxyethyl(meth)acrylate, ω-carboxyethyl acrylate, 2-(meth)acryloyl oxyethylsuccinic acid, 2-(meth)acryloyl oxyethyl hexahydrophthalic acid,hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and otherhydroxyalkyl (meth)acrylates, vinyl sulfonic acid, 4-styrene sulfonicacid, and the like. Carboxyl groups, hydroxyl groups, sulfonic acidgroups, and the like form hydrogen bonds that further strengthen thebond between the substrate layer and the basic adhesive layer; thus, itis advantageous to copolymerize these monomers.

Examples of crosslinking agents include difunctional or multifunctional(meth)acrylates, such as 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, ethylene glycol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol di(meth)acrylate,dipropylene glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, and other difunctional (meth)acrylates; and glyceroltri(meth)acrylate, trimethylol propane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,pentaerythritol tetra(meth)acrylate, and other multifunctional(meth)acrylates. Polymerizable oligomers such as urethane acrylate,polyester acrylate, and epoxy acrylate can also be used as crosslinkingagents. The use of a crosslinking agent increases the strength of theadhesive sheet while simultaneously allowing alkyl (meth)acrylatemonomers having low homopolymer Tg when polymerized in isolation, suchas ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and otheralkyl acrylate monomers, to be used to adjust the Tg of the acidic resinto within a desired range.

If an active hydrogen-containing acidic monomer and/or a crosslinkingagent is copolymerized, a (meth)acrylic resin can be obtained bycopolymerizing, for example, about 50 parts by mass or more, about 55parts by mass or more, or about 60 parts by mass or more and about 100parts by mass or less, about 95 parts by mass or less, or about 90 partsby mass or less of an alkyl (meth)acrylate monomer having from 1 to 30carbons at the ester site; about 2 parts by mass or more, about 5 partsby mass or more, or about 10 parts by mass or more and about 40 parts bymass or less, about 35 parts by mass or less, or about 30 parts by massor less of an active hydrogen-containing acidic monomer; and about 0.01parts by mass or more, about 0.02 parts by mass or more, or about 0.05parts by mass or more and about 5 parts by mass or less, about 3 partsby mass or less, or about 2 parts by mass or less of a crosslinkingagent.

The reinforcing fibers can be impregnated with the acidic (meth) acrylicresin by calender-molding. The acidic (meth) acrylic monomer can beconverted into a polymerizable oligomer by partially polymerizing(pre-polymerizing) it in advance and this partial polymerization ispreferably performed until the viscosity becomes approximately from 5 to10,000 mPa−s. Instead of using the pre-polymerized acid (meth) acrylicresin, acidic (meth) acrylic monomers with polymerization initiator canbe used to impregnate the reinforcing fibers.

The acidic resin may optionally have adhesive properties. For example,if the acidic resin is a pressure-sensitive adhesive or a hot-meltadhesive, an adhesive sheet can be disposed between two adherends tobond the adherends. It is also possible to bond the substrate layer toan adherend, and apply another layer or film, such as a decorative film,to the basic adhesive layer.

The mass ratio of the acidic resin and reinforcing fibers in thesubstrate layer is generally about 5 parts by mass or more, about 10parts by mass or more, or about 20 parts by mass or more and about 1,500parts by mass or less, about 1,300 parts by mass or less, or about 1,000parts by mass or less acidic resin per 100 parts by mass reinforcingfibers.

The thickness of the substrate layer is broadly determined by thethickness of the reinforcing fibers, and will generally be about 0.05 mmor more, about 0.1 mm or more, or about 0.15 mm or more, and about 1 mmor less, about 0.8 mm or less, or about 0.5 mm or less.

In addition to the acidic resin and the reinforcing fibers, thesubstrate layer may further comprise a filler, an antioxidant, a UVabsorber, or another optional ingredient.

The basic adhesive layer is disposed upon the substrate layer. Variousmaterials comprising nitrogen atom-containing functional groups, such asamino groups, amide groups, imino groups, nitrile groups, and the like,can be used as the basic adhesive. The basic adhesive may be apressure-sensitive adhesive or a hot-melt adhesive. If apressure-sensitive adhesive is used, the adhesive sheet can be bonded tothe adherend at normal temperatures, allowing the ease of application ofthe adhesive sheet to be improved. If a hot-melt adhesive is used, theadhesive sheet will generally be applied to an adherend while beingheated to about 100° C. or higher, about 120° C. or higher, or about150° C. or higher and about 200° C. or less, about 180° C. or less, orabout 170° C. or less, after which the adhesive sheet is cooled andbonded to the adherend.

Examples of basic adhesives include basic (meth)acrylic adhesives, basicepoxy adhesives, basic phenolic resin adhesives, basic urethaneadhesives, polyamide adhesives, nitrile rubber adhesives, and the like.

A basic (meth)acrylic adhesive, which is one type of favorable basicadhesive, can be obtained by polymerizing a mixture comprising an alkyl(meth)acrylate monomer having from 4 to 30 carbons at the ester site, abasic monomer, and a crosslinking agent, and is generally apressure-sensitive adhesive. Polymerization can be performed via thermalpolymerization or photopolymerization. Examples of possible initiatorsinclude thermal polymerization initiators known in the art, such asbenzoyl peroxide and azobis isobutyronitrile (AIBN), or photoinitiators,such as benzophenone and 2,2-dimethoxy-2-phenyl acetophenone.

Examples of alkyl (meth)acrylate monomers having from 4 to 30 carbons atthe ester site include n-butyl (meth)acrylate, isoamyl (meth)acrylate,n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl(meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl(meth)acrylate, and other alkyl (meth)acrylates; phenyl (meth)acrylate;methoxypropyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, and otheralkoxyalkyl (meth)acrylates; and phenoxyethyl (meth)acrylate and otherphenoxyalkyl (meth)acrylates. One or more types of these can be used inorder to obtain the desired adhesive properties.

A compound comprising an ethylenic unsaturated group and a nitrogenousgroup selected from the group consisting of an amino group, an amidegroup, an imino group, a nitrile group, an imide group, and combinationsthereof can be used as the basic monomer. Examples of basic monomersinclude 2-amino (meth)acrylate, N,N-dimethyl aminoethyl (meth)acrylate,2-diethyl aminoethyl (meth)acrylate, 1-(methylamino)ethyl(meth)acrylate, 2-(methylamino)ethyl (meth)acrylate, 1-(ethylamino)ethyl(meth)acrylate, 2-(ethylamino)ethyl (meth)acrylate,3-(dimethylamino)propyl (meth)acrylate, N-tert-butyl aminoethyl(meth)acrylate, (meth)acrylamide, dimethyl (meth)acrylamide, diethyl(meth)acrylamide, N-[3-(dimethyl amino)propyl] (meth)acrylamide, 2-vinylpyridine, 4-vinyl pyridine, dimethyl allylamine, diallyl methylamine andother compounds comprising an amino group or an amide group;3-hydroxy-4-(phenyl iminomethyl) phenyl (meth)acrylate, 4-[[(4-ethylphenyl) imino] methyl] phenyl (meth)acrylate, 4-[(4-ethoxyphenyl)iminomethyl] phenyl (meth)acrylate, 4-[[(4-butylphenyl)imino]methyl]phenyl (meth)acrylate, 3-hydroxy-4-[1-(phenylimino)ethyl] phenyl(meth)acrylate, and other compounds comprising an imino group;4-(4′-cyano-4-biphenylyl oxy) butyl (meth)acrylate,6-(4′-cyano-4-biphenylyl oxy) hexyl (meth)acrylate,2-[ethyl[4-(1,2,2-tricyano ethenyl) phenyl] amino] ethyl (meth)acrylate,8-(4′-cyanoazobenzen-4-yl oxy) octyl (meth)acrylate, and other compoundscomprising a nitrile group; and N-vinyl succinimide, N-vinylmaleinimide, N-vinyl phthalimide, N-(4-vinyl phenyl) maleinimide,N-[2-(vinyloxy) ethyl] phthalimide, N-(4-vinyl phenyl) phthalimide, andother compounds comprising an imide group. N-methyl diethanolaminedi(meth)acrylate, N-ethyl diethanolamine di(meth)acrylate, [(isopropylimino) bis(2,1-ethane diyl)] di(meth)acrylate, [(tert-butylimino)bis(2,1-ethane diyl)] di(meth)acrylate, and other nitrogenousmultifunctional (meth)acrylates can also be used; these also function ascrosslinking agents. Because highly basic nitrogenous groups increasethe strength of the bond with the acidic substrate layer, it isadvantageous to copolymerize a monomer comprising a highly basicnitrogenous group, such as an amino group, an imino group, or the like.

Examples of crosslinking agents include difunctional or multifunctional(meth)acrylates, such as 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, ethylene glycol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol di(meth)acrylate,dipropylene glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, and other difunctional (meth)acrylates; and glyceroltri(meth)acrylate, trimethylol propane tri(meth)acrylate,pentaerythritol tri(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,pentaerythritol tetra(meth)acrylate, and other multifunctional(meth)acrylates. Polymerizable oligomers such as urethane acrylate,polyester acrylate, and epoxy acrylate can also be used as crosslinkingagents.

A basic (meth)acrylic adhesive can be obtained by copolymerizing, forexample, about 50 parts by mass or more, about 55 parts by mass or more,or about 60 parts by mass or more and about 100 parts by weight or less,about 95 parts by mass or less, or about 90 parts by mass or less of analkyl (meth)acrylate monomer having from 4 to 30 carbons at the estersite; about 2 parts by mass or more, about 5 parts by mass or more, orabout 10 parts by mass or more and about 40 parts by mass or less, about35 parts by mass or less, or about 30 parts by mass or less of a basicmonomer; and about 0.01 parts by mass or more, about 0.02 parts by massor more, or about 0.05 parts by mass or more and about 5 parts by massor less, about 3 parts by mass or less, or about 2 parts by mass or lessof a crosslinking agent.

A polyamide adhesive, which is another favorable basic adhesive,comprises a polyamide obtainable via polycondensation of a polyaminewith a dibasic acid such as a dimer acid, polycondensation of anaminocarboxylic acid, ring-opening polymerization of a lactam, or thelike. Because polyamides are thermoplastic, polyamide adhesives aregenerally hot-melt adhesives.

The melt viscosity of a hot-melt polyamide adhesive at 160° C. isgenerally about 2,000 mPa·s or higher or about 2,500 mPa·s or higher,and about 6,000 mPa·s or lower or about 5,500 mPa·s or lower. The resinsoftening point of a hot-melt polyamide adhesive is generally about 80°C. or higher, about 100° C. or higher, or about 110° C. or higher, andabout 150° C. or lower, about 145° C. or lower, or about 135° C. orlower.

Tackifiers such as rosin, rosin ester, rosin phenol, terpene phenol andso on or plasticizer such as amide compound including N-ethylaminosulfonic acid amide and so on or ester compound including dibutylsebacate, dioctyl phthalate and so on, can be further added to thepolyamide adhesive. Adding a tackifier to the polyamide adhesiveincreases the glass transition temperature (Tg) of the polyamideadhesive, and also allows a solvent-type adhesive sheet to be obtained.

The thickness of the basic adhesive layer is generally about 0.01 mm ormore, about 0.015 mm or more, or about 0.02 mm or more, and about 0.2 mmor less, about 0.15 mm or less, or about 0.1 mm or less.

V-shaped, U-shaped, or other grooves may be disposed on the surface ofthe basic adhesive layer in a desired pattern, facilitating ventilationwhen the adhesive sheet is applied to an adherend. A linerrelease-treated with silicone or the like may be disposed upon the basicadhesive layer. The grooves in the surface of the basic adhesive layermay also be formed by furrows having V- or U-shaped or other groovedcross sections provided in the surface of the release liner.

The adhesive sheet can be prepared by forming a substrate layer ofreinforcing fibers impregnated with an acidic resin, and layering abasic adhesive layer thereupon.

If the acidic resin is a thermoplastic resin, the substrate layer can beformed by heating and melting the acidic resin, impregnating thereinforcing fibers with the melted resin, and cooling. Impregnation canbe performed via immersion, coating, spraying, or the like, immersionbeing preferable as it facilitates uniform impregnation. It is alsopossible to impregnate the reinforcing fibers with a solution of theacidic resin in acetone, methyl ethyl ketone, cyclohexanone, methylisobutyl ketone, cyclopentanone, dimethyl formamide, dimethyl acetamide,N-methyl pyrrolidone, or another solvent, and then remove the solvent toform the substrate layer. If the acidic resin is a thermoset resin or aUV-curing resin, the reinforcing fibers can be impregnated with apolymerizable mixture containing a monomer making up the acidic resinand a thermal polymerization initiator or photopolymerization initiator,and then heated or irradiated with radiation such as UV radiation or anelectron beam, thereby curing the polymerizable mixture and forming thesubstrate layer. It is also possible to prepare a polymerizable acrylicresin composition in which all or part of the monomer making up theacidic resin is pre-polymerized, impregnate the reinforcing fibers witha polymerizable mixture of a monomer, crosslinking agent, thermalpolymerization initiator, photopolymerization initiator, or the likeadded to the polymerizable acrylic resin composition as necessary, andthen heat or irradiate the fibers with radiation such as UV radiation oran electron beam to cure the polymerizable mixture and form thesubstrate layer. The pre-polymerization can be performed via either ofthermal polymerization or photopolymerization, and usable initiators areas described above.

If the basic adhesive layer comprises, for example, a (meth)acrylicadhesive, the polymerizable mixture comprising the monomer making up theadhesive and the thermal polymerization initiator or photoinitiator canbe heated or irradiated with radiation such as UV radiation or anelectron beam to cure, thereby forming a basic adhesive layer. It isalso possible to prepare a polymerizable acrylic resin composition inwhich all or part of the monomer making up the adhesive ispre-polymerized, and then heat or irradiate a polymerizable mixture of amonomer, crosslinking agent, thermal polymerization initiator,photopolymerization initiator, or the like added to the polymerizableacrylic resin composition as necessary with radiation such as UVradiation or an electron beam to cure the polymerizable mixture and formthe basic adhesive. The pre-polymerization can be performed via eitherof thermal polymerization or photopolymerization, and usable initiatorsare as described above. If the basic adhesive layer comprises a hot-meltadhesive such as a polyamide adhesive, the hot-melt adhesive can beheated, melted, and molded into a sheet to form the basic adhesivelayer. The basic adhesive layer can also be formed by impregnating thereinforcing fibers with a solution of basic adhesive, and then removingthe solvent.

The adhesive sheet may further comprise an addition layer, such as adecorative layer or a gas barrier layer.

The adhesive sheet can be applied to a flat or curved surface of anadherend, such as a floor slab, to reinforce or repair the adherend orprevent crumbling of part of the adherend. In accordance with anembodiment of the present disclosure, a reinforcing repair tapecomprising an adhesive sheet is provided. Putting the adhesive sheetinto the form of a reinforcing repair tape allows for easy applicationto a three-dimensional adherend, such as lining a cylindrical orprism-shaped adherend.

In an embodiment of the present disclosure, the reinforcing repair tapeis used as a building material-reinforcing repair tape. Examples ofbuilding materials to which the reinforcing repair tape can be appliedinclude bridge piers, concrete pillars of buildings or the like,smokestacks, slabs, and the like. The lengthwise direction of thereinforcing repair tape is aligned with the circumferential direction ofthe adherend, and can be wrapped one or more times around thecircumference of the building material. The tape shape allows tension tobe applied as the tape is wrapped.

The reinforcement of a concrete pillar will be described with referenceto FIGS. 2 to 4 as an example of using the building material-reinforcingrepair tape. FIG. 2 is a perspective view of a concrete pillar 30reinforced by wrapping a reinforcing repair tape 20. FIG. 3 is across-sectional view of the concrete pillar 30 with the reinforcingrepair tape 20 wrapped twice therearound (the first wrapping beinglabeled 20 and the second wrapping being labeled 20′), and FIG. 4 is amagnified view of the part indicated by dotted lines in FIG. 3.

The surface is prepared by grinding the surface of the concrete pillar30, the reinforcing repair tape 20 is disposed so that the layer ofbasic adhesive 18 faces the concrete pillar 30, and the reinforcingrepair tape 20 is wrapped around the circumference of the concretepillar 30, while tension is evenly applied thereto. Disposing the basicadhesive layer so as to face the concrete pillar allows for theprevention of reductions in strength due to neutralization of thesurface of the concrete.

Reinforcing/repairing effects can be obtained via a single wrapping, butthe tape may also be wrapped two or more times, as shown in FIGS. 3 and4. Wrapping the reinforcing repair tape two or more times yields aconstricting effect due to the tension upon the reinforcing repair tape20. Here, “constricting effect” refers to an improvement in thestrength, especially the compressive strength, of the reinforcedbuilding material or other adherend in a direction orthogonal to thedirection in which the reinforcing repair tape is tightened (i.e., thedirection in which tension is applied) due to the circumference of theadherend being bound by the reinforcing repair tape. In order to obtaina greater constricting effect, it is preferable that the lengthwisedirection of the reinforcing fibers (for example, the warp fibers orfilling fibers) be disposed in parallel to the tightening direction.

In addition, wrapping the reinforcing repair tape two or more times, asshown in FIG. 4, leads to contact between the acidic resin 16 of thefirst wrap and the basic adhesive 18′ of the second wrap. As a result,the acid-base interaction of the acidic resin 16 and the basic adhesive18′ strengthens the bond between the first wrap and the second wrap,heightening integrity between the first and second wraps, and furtherimproving shear strength in a direction parallel to the surface of thereinforcing repair tape. Thus, in accordance with the presentdisclosure, a building material such as a concrete pillar or a bridgepier can be imparted with the desired degree of compressive strength bywrapping the reinforcing repair tape multiple times around the buildingmaterial, under tension.

The present invention is capable of reinforcing a building material,such as a concrete pillar or bridge pier, in isolation, or it can alsobe used for reinforcement in combination with existing methods suchadhesive impregnation, sheet steel lining, frame reinforcement viareinforced concrete, or the like.

Example

In the following examples, specific embodiments of the presentdisclosure are exemplified, but the present invention is not restrictedthereto. All parts and percentages are by mass unless otherwiseindicated.

The materials used in these examples are shown below in Table 1.

TABLE 1 Trade name or abbreviation Description Supplier 2EHA2-ethylhexyl acrylate Nippon Shokubai Co., Ltd. AA Acrylic acid ToagoseiCo., Ltd. HDDA 1,6-hexanediol diacrylate Kyoeisha Chemical Co., Ltd. IOAIsooctyl acrylate 3M Company DMAA N,N-dimethylacrylamide Kohjin Irgacure651 Photopolymerization initiator BASF (former Ciba2,2-dimethoxy-2-phenylacetophenone Specialty Chemicals) 3M 3779Scotch-Weld ™ hot-melt adhesive 3M Company Polyamide-based Haritac F85Stabilized rosin ester tackifier Harima Chemicals Group, Inc. Torayca ®cloth Carbon fibers, plain weave Toray Industries, Inc. CO6343 Thickness250 μm, mass 198 g/m² Tensile strength 1.80 kN/mm² Breaking elongation2% Fibrasheet AK10/10 Aramid fibers, bidirectional knitted Fibex Co.,Ltd. sheet Thickness 480 μm, mass 180 g/m² Tensile strength 2.10 kN/mm²Breaking elongation 4% KTV 7446Y Vinylon fibers, triaxial fabric NittoBoseki Co., Ltd. Thickness 360 μm, mass 42 g/m² Tensile strength 0.02kN/mm² Breaking elongation 5% KS 2810 Glass fibers, plain weave NittoBoseki Co., Ltd. Thickness 360 μm, mass 395 g/m² Tensile strength 0.16kN/mm² Breaking elongation 5%

<Test Methods> (1) Glass Transition Temperature

Glass transition temperature was measured via differential scanningcalorimetry (DSC Q2000, TA Instruments). About from 5 to 15 mg of asample was placed within a dedicated aluminum vessel, and differentialscanning calorimetry was performed in an inert gaseous atmosphere over atemperature range from −100° C. to 150° C. at a temperature increaserate of 10° C./minute. Measurement was performed twice in a row, and theglass transition temperature was determined from the results of thesecond measurement.

(2) Compression Test

A 25 mm-diameter, 50 mm-height cylindrical test concrete pillar wasprepared using mortar (premix mortar M130, Yoko Bussan). Specifically,100 parts by mass of M130 and 15.6 parts by mass of water were quicklymixed, and the mixed mortar was poured into a cylindrical mold. Next,the mortar was cured for 72 hours at a temperature of 25° C. and arelative humidity of 90%. After curing, the concrete pillar was removedfrom the mold, the surface of the mortar was washed with water, and theconcrete pillar was thoroughly dried. An adhesive sheet cut to a widthof 50 mm was wrapped twice around the obtained concrete pillar undertension so that the basic adhesive layer thereof faced the concretepillar, after which the whole was cured for three days at 23±1° C. tocreate a test piece.

The obtained test piece was sandwiched between two 15 cm-diameter, 2cm-thickness steel plates, placed in a tensilon tester (RTC-1325A;Orientec Co., Ltd.), and compressed in the height direction at atemperature of 25±3° C. at a compression speed of 1 mm/minute to measurecompression strength (N/test piece). Values were obtained for themaximum value for compression strength and for the average value forcompression strength (average compression strength) after a further 5 mmof compression was reached from the displacement value when the maximumvalue was reached.

<Preparing Reinforcing Fiber Sheet (Substrate Layer) Impregnated withAcidic Resin AR1>

70 parts by mass of 2-ethylhexyl acrylate (2EHA), 30 parts by mass ofacrylic acid (AA), 0.14 parts by mass of Irgacure 651, and 1.0 parts bymass of 1,6-hexanediol diacrylate (HDDA) were introduced simultaneouslyinto a planetary mixer and kneaded under reduced pressure (50 mmHg) for15 minutes to obtain a polymerizable acrylic resin composition. Thepolymerizable acrylic resin composition is pre-polymerized acrylic resincomposition.

The obtained polymerizable acrylic resin composition and one type ofreinforcing fiber sheet selected from Torayca® cloth CO6343 (carbonfibers), Fibrasheet AK 10/10 (aramid fibers), KTV 7446Y (vinylonfibers), or KS 2810 (glass fibers) were sandwiched between two sheets ofsilicone-treated PET film and impregnated and calender-molded into asheet shape.

The molded piece was further retained inside the two sheets ofsilicone-treated PET film, and both sides of the sheet were irradiatedwith UV radiation for two minutes apiece at an irradiation intensity of0.3 mW/cm², and then for two minutes at an irradiation intensity of 6.0mW/cm² to cure the composition, thus preparing an acidic resinAR1-impregnated reinforcing fiber sheet (substrate layer). Reinforcingfiber sheets impregnated with acidic resins AR2 through AR5 weresimilarly prepared, using Torayca® cloth CO6343 as the reinforcingfibers, in a manner similar to that of the acidic resin AR1-impregnatedreinforcing fiber sheet, except that the composition of the acidicresins were as shown in table 2. A specimen for measuring the glasstransition temperature of the acidic resin was prepared using a part ofthe completed reinforcing fiber sheet.

TABLE 2 Acidic resin (AR) compositions Acidic resin (AR) 2EHA AAIrgacure 651 HDDA AR1 70 30 0.14 1.0 AR2 70 30 0.14 0.08 AR3 80 20 0.140.08 AR4 90 10 0.14 0.08 AR5 100 0 0.14 0.08

<Preparing Basic Adhesive Layer BA1>

67.5 parts by mass of isooctyl acrylate (IOA), 2.5 parts by mass of AA,0.14 parts by mass of Irgacure 651, 0.08 parts by mass of HDDA, and 30parts by mass of N,N-dimethyl acrylamide (DMAA) were introducedsimultaneously into a planetary mixer and kneaded for 15 minutes underreduced pressure (50 mmHg) to obtain a polymerizable acrylic resincomposition. The polymerizable acrylic resin composition ispre-polymerized acrylic resin composition.

The obtained polymerizable acrylic resin composition was sandwichedbetween two sheets of silicone-treated PET film to yield a totalthickness of 0.05 mm, and calender-molded into a sheet shape.

The molded piece was further retained inside the two sheets ofsilicone-treated PET film, and both sides of the sheet were irradiatedwith UV radiation for two minutes apiece at an irradiation intensity of0.6 mW/cm², and then for two minutes at an irradiation intensity of 6.0mW/cm² to cure the composition, after which one sheet ofsilicone-treated PET film was removed to prepare a basic adhesive layerupon a silicone-treated PET film carrier. A specimen for measuring theglass transition temperature of the basic adhesive was prepared byremoving the silicone-treated PET film and cutting a part of thecompleted basic adhesive sheet.

<Preparing Basic Adhesive Layer BA2 (Hot-Melt Adhesive Layer)>

A polyamide resin for hot-melt adhesives (3779, 3M Company) was cut intoa small strip using a cutter knife, and the small polyamide strip wasplaced upon a 90 μm-thick paper liner having a release-treated surface.Some 0.05 mm iron spacers were placed around the small polyamide stripupon the paper liner, and a paper liner having a release-treated surfacewas placed upon the small polyamide strip and the iron spacers,sandwiching the polyamide resin and the iron spacer therebetween.

The laminate was heat-pressed at 180° C. for 30 seconds using a heaterplate press device (N5042; NPa System Co., Ltd.), after which onerelease-treated paper liner was removed to obtain a 0.05 mm-thickhot-melt basic adhesive layer. A specimen for measuring the glasstransition temperature of the hot-melt basic adhesive was prepared byremoving the paper liner and cutting a part of the completed basicadhesive sheet.

<Preparing Basic Adhesive Layer BA3 (Solvent-Based Adhesive Layer)>

100 parts by mass of a 1:1 mixed solvent of toluene and isopropylalcohol were introduced into a lidded glass vessel, and 25 parts by massof a polyamide resin for hot-melt adhesives (3779, 3M Company) and 15parts by mass of a rosin ester tackifier (Haritac F85; Harima ChemicalsGroup) were added thereto. After thoroughly stoppering the vessel,heating was performed in a 65° C. oven for 12 hours to obtain a liquidpolyamide dispersion.

The liquid dispersion was applied to a 0.09 mm-thick paper liner havinga release-treated surface to obtain a solvent-based basic adhesive layerhaving a post-drying (65° C. oven for 3 minutes and 100° C. oven for 3minutes) thickness of the adhesive layer of 0.05 mm. A specimen formeasuring the glass transition temperature of the solvent-based basicadhesive was prepared by removing the paper liner and cutting a part ofthe completed basic adhesive sheet.

<Preparing Adhesive Sheet>

The acidic resin-impregnated reinforcing fiber sheet and the basicadhesive layer were layered and cured at 23±1° C. for at least threedays to prepare an adhesive sheet. The results of a compression testperformed upon the obtained adhesive sheet and the results of acompression test performed upon a concrete pillar to which no adhesivesheet was applied constituting a comparative example 1 are shown.Adhesive sheets comprising basic adhesive layers BA2 and BA3 wereapplied to a concrete pillar while being heated by a dryer. The glasstransition temperatures (Tg) of the acidic resins AR1 to 5 and the basicadhesive layers BA1 to 3 are presented together in table 3. A chart forthe compression test performed on example 1 and comparative example 1 isshown in FIG. 5.

TABLE 3 Compression test (kN/test piece) Substrate layer Basic adhesiveThickness (mm) Average Acidic resin (AR) Reinforcing layer (BA)Substrate Adhesive Maximum compression Type Tg (° C.) fibers Type Tg (°C.) layer BA sheet value strength Example 1 AR1 21 CO6343 BA1 −7 0.350.05 0.40 21.0 7.0 Example 2 BA2 −5 0.35 0.05 0.40 17.2 9.4 Example 3BA3 16 0.35 0.05 0.40 16.0 7.3 Example 4 AK10/10 BA1 −7 0.58 0.05 0.6318.6 13.1 Example 5 KTV 7446Y 0.47 0.05 0.52 8.2 4.5 Example 6 KS 28100.46 0.05 0.51 13.2 10.7 Example 7 AR2 15 CO6343 0.35 0.05 0.40 18.0 7.0Example 8 AR3 −20 0.35 0.05 0.40 12.8 9.1 Example 9 AR4 −51 0.35 0.050.40 11.1 7.8 Example 10 AR5 −71 0.35 0.05 0.40 10.5 2.9 Comparative — —— — — — — — 7.7 — example 1

REFERENCE NUMERALS

-   10 Adhesive sheet-   12 Substrate layer-   14 Reinforcing fibers-   16, 16′ Acidic resin-   18, 18′ Basic adhesive-   20, 20′ Reinforcing repair tape-   30 Concrete pillar

1. An adhesive sheet comprising a substrate layer comprising reinforcingfibers impregnated with an acidic resin and a basic adhesive layerdisposed upon the substrate layer.
 2. The adhesive sheet according toclaim 1, wherein the acidic resin has a Tg of −60° C. or higher.
 3. Theadhesive sheet according to claim 1, wherein the basic adhesive layercomprises a pressure-sensitive adhesive or a hot-melt adhesive.
 4. Theadhesive sheet according to any one of claim 1, wherein the reinforcingfibers have a tensile strength of 0.01 kN/mm² or more and a breakingelongation of 10% or less as measured according to JIS A 1191:2004.
 5. Areinforcing repair tape comprising the adhesive sheet described in anyone of claim
 1. 6. A building material-reinforcing repair tapecomprising the adhesive sheet described in any one of claim
 1. 7. Areinforced building material around which the buildingmaterial-reinforcing repair tape described in claim 6 is wrapped.
 8. Thereinforced building material according to claim 7, around which thebuilding material-reinforcing repair tape is wrapped two or more times.9. A method of manufacturing a reinforced building material, the methodcomprising a step of wrapping the building material-reinforcing repairtape described in claim 6 around the circumference of a buildingmaterial, under tension.